1. Technical Field
The present invention relates to an apparatus for spraying an etchant onto a printed circuit board and a method for using such an apparatus to etch a printed circuit board.
2. Discussion of Related Art
Recently, as the electronic appliances are becoming smaller in size and diversified in function, printed circuit boards (PCBs) widely used in such electronic appliances are required to have higher circuit density and reliability.
Usually, a chemical etching process is used for etching a conductive pattern on a copper clad laminate (CCL) as described below. First, a photoresist layer is applied on the CCL by screen printing method. Second, the CCL is driven to pass through an etching bath by a feed roller, thereby an etchant is sprayed simultaneously and evenly onto both an upper surface and a bottom surface of the CCL by a number of spray nozzles. As a result, the copper layer uncovered by the photoresist layer is etched and a conductive pattern is formed on the copper layer.
This chemical etching process is both cheap and can involve a high level of automation. However, chemical etching also suffers from a problem known as “the puddle effect”. Specifically, “the puddle effect” is due to different refresh rates of etchant between a peripheral area and a central area of the CCL being sprayed, i.e., the refresh rate of etchant in peripheral area is higher than that in central area due to the formation of a puddle of etchant in a central area of the CCL during spraying process. Thus, “the puddle effect” causes different etching speeds between peripheral areas and central areas of an upper surface of the CCL. As a result, the peripheral areas are etched more deeply than the central areas.
Therefore, there is a desire to develop a new apparatus and method for etching a printed circuit board that can overcome the “the puddle effect”.